Aromatic Hydrocarbon

To determine the value of "s" according to Hückel's rule for the given aromatic molecule, follow these steps:
1. **Hückel's Rule**: A molecule is aromatic if it has electrons, where is a non-negative integer (0, 1, 2, ...).
2. **Count the Electrons**: Examine the depicted molecule and identify the double bonds to count the electrons. There are 14 electrons in this molecule.
3. **Apply Hückel's Rule**: Set . Solve for .



Thus, the value of "s" is 3.
Therefore, according to Hückel's rule, the value of "s" is 3.

To determine which of the given compounds are aromatic, we need to verify the following aromaticity criteria:

1. The molecule must be cyclic.
2. The molecule must be planar or flat, allowing for maximum overlap of the p-orbitals.
3. The molecule must have a complete delocalization of the π-electrons in the ring.
4. The molecule must follow Hückel's Rule, which states that the molecule must have (4n + 2) π-electrons, where n is a non-negative integer (0, 1, 2, 3, etc.).

Now, let's examine each option to identify which compounds are aromatic:

Compound 1: This compound is not aromatic because it does not satisfy all the aromaticity criteria. It might be cyclic and planar, but it doesn't meet the (4n + 2) π-electron rule for aromaticity.

Compound 2: This compound is aromatic. It is cyclic, planar, and has complete delocalization of π-electrons. Additionally, it satisfies Hückel's rule with (4n + 2) π-electrons, for example, with n = 1.

Compound 3: This compound is not aromatic. While it may be cyclic, it fails to meet the necessary criteria for π-electron delocalization or the (4n + 2) rule.

Compound 4: This compound is aromatic. It is cyclic, allows for π-electron delocalization, is planar, and also satisfies Hückel's rule, having (4n + 2) π-electrons with n=1 or another valid integer.

Conclusion: Based on the analysis, the aromatic compounds are:

Compound 2 and Compound 4.